[RUST/HOUND] WavWriter 구조체 : write_sample 메소드를 사용해 FM(Frequency Modulation) 음원 WAV 파일 생성하기

■ WavWriter 구조체의 write_sample 메소드를 사용해 FM(Frequency Modulation) 음원의 WAV 파일을 생성하는 방법을 보여준다.

▶ Cargo.toml


[package]
name = "test_project"
version = "0.1.0"
edition = "2021"

[dependencies]
hound = "3.4.0"

[package]

name = "test_project"

version = "0.1.0"

edition = "2021"

[dependencies]

hound = "3.4.0"

▶ src/fm.rs


use std::f32::consts;

pub const SAMPLE_RATE : f32 = 44100.0;

pub struct Note
{
    pub scale  : i32,       // 음계
    pub length : isize,     // 음표 길이
    pub gain   : f32,       // 음량
    pub params : (f32, f32) // 음색 매개변수
}

pub fn make_fm(wave_vector : &mut Vec<f32>, note : Note)
{
    let frequency : f32 = get_frequency(note.scale);

    let a : f32 = 2.0 * consts::PI * frequency / SAMPLE_RATE;

    let wave_vector_length : usize = note.length as usize;

    let mut temporary_wave_vector1 :Vec<f32> = vec![0.0; wave_vector_length];

    for i in 0..(note.length as usize)
    {
        let t : f32 = i as f32;

        let sin1 : f32 = note.params.0 * (a * t).sin();
        let sin2 : f32 = note.params.1 * (a * t + sin1).sin();
        let sin3 : f32 = (a * t + sin2).sin();

        temporary_wave_vector1[i] = sin3;
    }

    let attack  : usize = 3;
    let decay   : usize = attack + 200;
    let sustain : f32 = 0.90;
    let release : usize = (wave_vector_length as f32 * 0.4) as usize;

    let temporary_wave_vector2 : Vec<f32> = temporary_wave_vector1.into_iter().enumerate().map
    (
        |(index, value)|
        {
            let v1 : f32 = (value * note.gain) as f32;

            if index < attack { return index as f32 / attack as f32 * v1; }

            let v2 : f32 = v1 * sustain;

            if index < decay
            {
                let dec : f32 = (1.0 - (index as f32 / decay as f32)) * (1.0 - sustain) * v1.abs();

                return if v2 > 0.0 { v1 + dec } else { v1 - dec }
            }
            else if index > (wave_vector_length - release)
            {
                let i : usize = index - (wave_vector_length - release);

                return (1.0 - i as f32 / release as f32) * v2;
            }

            return v2;
        }
    ).collect();

    wave_vector.extend(temporary_wave_vector2);

}

// bpm  : 분당 박자, beats per minute
// note : 음표 예) 4(4분 음표)
pub fn calculate_note_length(bpm : usize, note : usize) -> isize
{
    return ((4.0 / note as f32) * (60.0 / bpm as f32) * SAMPLE_RATE) as isize;
}

// scale : 음계, 예) 60(도), 64(미), 67(솔)
fn get_frequency(scale : i32) -> f32
{
    return 440.0 * 2.0f32.powf((scale - 69) as f32 / 12.0);
}

use std::f32::consts;

pub const SAMPLE_RATE : f32 = 44100.0;

pub struct Note

{

pub scale : i32, // 음계

pub length : isize, // 음표 길이

pub gain : f32, // 음량

pub params : (f32, f32) // 음색 매개변수

}

pub fn make_fm(wave_vector : &mut Vec<f32>, note : Note)

{

let frequency : f32 = get_frequency(note.scale);

let a : f32 = 2.0 * consts::PI * frequency / SAMPLE_RATE;

let wave_vector_length : usize = note.length as usize;

let mut temporary_wave_vector1 :Vec<f32> = vec![0.0; wave_vector_length];

for i in 0..(note.length as usize)

{

let t : f32 = i as f32;

let sin1 : f32 = note.params.0 * (a * t).sin();

let sin2 : f32 = note.params.1 * (a * t + sin1).sin();

let sin3 : f32 = (a * t + sin2).sin();

temporary_wave_vector1[i] = sin3;

}

let attack : usize = 3;

let decay : usize = attack + 200;

let sustain : f32 = 0.90;

let release : usize = (wave_vector_length as f32 * 0.4) as usize;

let temporary_wave_vector2 : Vec<f32> = temporary_wave_vector1.into_iter().enumerate().map

(

|(index, value)|

{

let v1 : f32 = (value * note.gain) as f32;

if index < attack { return index as f32 / attack as f32 * v1; }

let v2 : f32 = v1 * sustain;

if index < decay

{

let dec : f32 = (1.0 - (index as f32 / decay as f32)) * (1.0 - sustain) * v1.abs();

return if v2 > 0.0 { v1 + dec } else { v1 - dec }

}

else if index > (wave_vector_length - release)

{

let i : usize = index - (wave_vector_length - release);

return (1.0 - i as f32 / release as f32) * v2;

}

return v2;

}

).collect();

wave_vector.extend(temporary_wave_vector2);

}

// bpm : 분당 박자, beats per minute

// note : 음표 예) 4(4분 음표)

pub fn calculate_note_length(bpm : usize, note : usize) -> isize

{

return ((4.0 / note as f32) * (60.0 / bpm as f32) * SAMPLE_RATE) as isize;

}

// scale : 음계, 예) 60(도), 64(미), 67(솔)

fn get_frequency(scale : i32) -> f32

{

return 440.0 * 2.0f32.powf((scale - 69) as f32 / 12.0);

}

▶ src/main.rs


mod fm;

use std::fs;
use std::io;

use hound;

fn main()
{
    let wav_spec : hound::WavSpec = hound::WavSpec
    {
        channels        : 1,
        sample_rate     : fm::SAMPLE_RATE as u32,
        bits_per_sample : 32,
        sample_format   : hound::SampleFormat::Float
    };

    let mut wav_writer : hound::WavWriter<io::BufWriter<fs::File>> = hound::WavWriter::create("d:/fm.wav", wav_spec).unwrap();

    let mut wave_vector : Vec<f32> = vec![];

    let bpm         : usize  = 120;
    let note_length : isize = fm::calculate_note_length(bpm, 4);

    let parameter_array : [(f32, f32); 4] = [(4.5, 2.0), (7.0, 3.0), (3.0, 2.0), (11.0, 4.0)];

    for parameter in parameter_array
    {
        for scale in [60, 64, 67, 64, 60, 64, 67, 72]
        {
            fm::make_fm(&mut wave_vector, fm::Note { scale, length: note_length, gain: 0.5, params: parameter});
        }
    }

    for v in wave_vector.into_iter()
    {
        wav_writer.write_sample(v).unwrap();
    }
}

mod fm;

use std::fs;

use std::io;

use hound;

fn main()

{

let wav_spec : hound::WavSpec = hound::WavSpec

{

channels : 1,

sample_rate : fm::SAMPLE_RATE as u32,

bits_per_sample : 32,

sample_format : hound::SampleFormat::Float

};

let mut wav_writer : hound::WavWriter<io::BufWriter<fs::File>> = hound::WavWriter::create("d:/fm.wav", wav_spec).unwrap();

let mut wave_vector : Vec<f32> = vec![];

let bpm : usize = 120;

let note_length : isize = fm::calculate_note_length(bpm, 4);

let parameter_array : [(f32, f32); 4] = [(4.5, 2.0), (7.0, 3.0), (3.0, 2.0), (11.0, 4.0)];

for parameter in parameter_array

{

for scale in [60, 64, 67, 64, 60, 64, 67, 72]

{

fm::make_fm(&mut wave_vector, fm::Note { scale, length: note_length, gain: 0.5, params: parameter});

}

for v in wave_vector.into_iter()

{

wav_writer.write_sample(v).unwrap();

}

test_project.zip